Table 2.
Ionic Selectivity of Wild-type KCNKØ and KCNKΔ299-1001 Channels
| Erev, mV(PK/PX) | ||
|---|---|---|
| Wild-type KCNKØ | KCNKΔ299-1001 | |
| Li+ | −118 ± 9 | −126 ± 3 |
| (148 ± 23) | (160 ± 12) | |
| Na+ | −118 ± 10 | −122 ± 6 |
| (149 ± 15) | (150 ± 2) | |
| Cs+ | −72 ± 8 | −74 ± 5 |
| (23 ± 4) | (22 ± 2) | |
| Rb+ | −36 ± 5 | −32 ± 2 |
| (5 ± 1) | (3.7 ± 0.1) | |
| K+ | −12 ± 1 | −7 ± 1 |
| (1.5 ± 0.1) | (1.3 ± 0.1) | |
Whole-cell macroscopic reversal potentials in millivolts (Erev) were measured by two-electrode voltage clamp under nearly bi-ionic conditions with 100 mM of the indicated cation in the external solution. To measure wild-type KCNKØ channel currents, oocytes were fully activated by 20-min preincubation in 50 nM PMA. Values represent the mean ± SEM of four oocytes. Permeability ratios (shown in parentheses) were approximated according to: PK/PX = exp(−FErev/RT), where Pk and Px represent the permeability of potassium and the test cation, respectively.